The
general consensus seems to be that automatic transmissions are better for
plowing snow, for many reasons. I will not go into them here. What I’d like to
talk about is how to keep them operable, while using them to plow snow, and tow.
Since I plow with an auto myself, and burned one up (in a sense), I’d like to
help you NOT burn yours up with some suggestions. When I had my GM TH350 rebuilt
two years ago, it cost me about $1,000. Most automatic transmissions work the
same way, and most of the principles are the same. I am going to generalize in
my recommendations. Some of your trucks may already have some of the features
I’m going to talk about, and some of you should add these features. Some of
you may also know the tips I’m about to recommend too.

The worst
enemy of an automatic transmission is HEAT.
It’s common for transmission fluid temperatures to exceed 350 degrees. A
“normal” operating temperature would be approximately 200 degrees. I’ve
actually seen a transmission that caught fire due to overheating! Anything you
can do to help your trans run cooler will extend its life. One simple thing you
can do, is not shut your truck off after heating up the trans. One way of
heating up the trans rapidly would be pulling a trailer up a long steep hill.
Shutting the truck off when you get to the top to say, “mow a lawn” would be
a bad thing, the same as towing a boat up a long boat ramp, then parking the
truck in a parking lot at the top, and shutting it off. Plowing a driveway, and
shutting the truck off to shovel the walks is a bad practice to get into. The
same as plowing a parking lot, and shutting the truck off while you go grab a
cup of coffee is not a good idea. When you shut the truck off, the trans fluid
stops circulating through the cooler. Letting the truck idle for say 10 minutes,
or more, or maybe even less (depending on the vehicle) will help bring the
transmission fluid temperature down. This is also why it’s a good idea to keep
a full or near full tank of fuel. Many of us never shut our trucks off when
plowing, myself being one of them. In addition to plowing, just running your
truck in 4wd generates more heat than normal. Add to it driving in 6” of snow
or more, and that’s even more of a strain, which generates more heat.
Especially heavy wet snow, it gives more resistance to your tires, which makes
the trans run hotter. The extra weight of the blade on the truck, and ballast in
the back adds to it all too.

There are
a few things to keep in mind about automatic transmissions. When you drain the
fluid in the pan only, you are only draining a small percentage of the total
amount of fluid in the transmission. For example: The GM TH350 transmission
holds approximately 21.5 pints (about 11 quarts) of fluid. Draining the fluid in
the pan only removes about 8 pints (4 quarts). This means that inside the
transmission and torque converter, there is still 7 quarts of fluid. So in this
case, you’d be changing less than half of the fluid. For the half hour or less
it takes to drain and add 4 quarts, it’s worth it. Compare the cost of time
and fluid to having your transmission rebuilt, and you’ll see the savings
potential. You could drain the four quarts, run the truck for a day, and drain
the pan again, adding another 4 quarts. This will replace much of the fluid with
fresh fluid. It will be “diluted” fresh fluid, but it’s still cheap
insurance against having your transmission rebuilt. Fluid should be drained when
the transmission is hot, never “first thing in the morning”. The main reason
most trans pans don’t have a drain plug, is because if they did, many people
would just drain the four quarts, and think they just changed all the fluid in
the transmission. It’s also because most people wouldn’t remove the fluid
pan, and change the filter or filter screen as well as the fluid. It’s
possible for you to drain the fluid in the torque converter yourself, but it’s
a much more difficult job than just draining the fluid in the pan. Not only
that, but if you want to go that far, you should have your transmission flushed
at a reputable shop.

What you can do

There are
a few modifications you can make to help your transmission last longer, aside
from letting your truck idle after putting a load on the transmission.

Add
a transmission fluid drain plug. This will allow you to drain some of the
fluid in your shop or driveway, and replace it with fresh fluid. There are
universal drain plug kits sold in most auto parts stores. All you have to do
is remove the pan on the bottom of the transmission, drill a hole, and
install the drain plug kit. The kits sell for about seven dollars. Adding a
drain plug makes it a much neater job for you to drain the fluid, remove the
trans pan, and change the filter and gasket as well. If you have your
transmission serviced at a shop, and want to service it yourself in the
future, having them add a drain plug will make it a cleaner job for you to
do yourself in the future.

Add
a magnet inside the trans pan. You could also add one on the outside, on the
bottom of the pan. It’s less likely to stay there, as opposed to adding
one inside the pan. Inside the pan it will stay in place, and can’t harm
anything. Most late model transmissions have a magnet in them already.
Chrysler and Dodge have used them since the 70’s. If you see a small round
“dimple” in the surface of the trans pan, it’s to help hold the magnet
inside in place. The magnet catches metal particles, and stops them from
circulating through the transmission, reducing wear.

Add
a transmission cooler. Most vehicles already have a cooler built into the
radiator. This is usually not enough to significantly cool the fluid,
considering it will never get cooled below the engine coolant temperature.
Not only that, but the built in cooler may even cause the engine to run
hotter, because the trans fluid can be as hot as 350 degrees, and the engine
typically runs at about 200 degrees. When adding a second cooler, you want
the fluid to go through the cooling coil inside the radiator, then out and
through the auxiliary cooler, then back to the transmission.

Change
your fluid more often than recommended in the owner’s manual. For example,
my factory service manual for my truck recommends a transmission fluid
change every 24,000 miles under “normal” use. It recommends a fluid
change after every 12,000 miles of heavy-duty use, such as towing and heavy
stop and go traffic in the summertime. When I cooked my transmission, it had
less than 3,000 miles on it. I plowed 14 storms in those 3,000 miles. It’s
hard to say how many hours I actually plowed for, but an educated guess
would be about 65 hours of actual “plow time”.

You
could add an aftermarket transmission fluid temperature gauge, and monitor
the temperature of your transmission. This is a bit extreme, but many people
have added them.

Keep
the outside of your transmission clean. A build up of grease and grime can
catch fire when you really don’t want it to! The grease helps insulate the
transmission housing, reducing it’s ability to dissipate heat. This is why
most automatic transmissions are made of aluminum, besides the fact that
they weigh less.

You
can actually buy a larger transmission oil pan, to increase the fluid
capacity of the system. More fluid means the transmission will run cooler.

Don’ts

Never
replace steel transmission cooler lines with copper tubing or aluminum
tubing. If a line bursts, all of the transmission fluid will be pumped out
in a matter of minutes. The transmission will be overheated, and need to be
rebuilt.

Substitute
draining the fluid from the pan for having the transmission filter replaced
and the transmission flushed at a reputable shop at the intervals
recommended in your owners manual for “severe duty”, or “commercial
use”, or slightly more often.

Connect
an auxiliary transmission fluid cooler before the cooling coil in the
radiator.

Wait
too long to have your transmission fluid changed after plowing for many
hours. It’s cheaper to spend the money to have the transmission serviced,
than to pay to have it rebuilt. I would consider “many hours” to be 60
hours of actual plowing time. The $100 or less to have the trans serviced is
A LOT cheaper than the $1000+ to have it rebuilt.

Add
synthetic fluid to your transmission fluid. If you want to use synthetic
fluid, have a shop drain and flush your transmission, and refill it with
only synthetic fluid.

Shift
the transmission while the truck is moving. ALWAYS come to a FULL STOP
before shifting from forward to reverse. This is the main reason automatic
transmissions fail after or while being used for plowing. It’s not that
the transmission can’t handle plowing; it’s the operator often
unknowingly “abusing” the transmission by shifting while moving. This
can easily destroy a transmission over time, often a short period of time.

Ignore
transmission fluid leaks. Get them repaired ASAP. Running an automatic
transmission while it’s low on fluid can severely reduce the
transmission’s service life.

Use
the truck with a low transmission fluid level. Be sure it’s in the
“OK” range on the dipstick.